Shock wave lithotripsy (SWL) is not able to treat all urinary stones. Identifying stones as susceptible or resistant to SWL at diagnosis would allow treatment that spares patients from unnecessary SWL, thereby reducing the chance of SW-induced injury. Our hypothesis: Presently available imaging techniques"utilized correctly'have the capability of predicting the susceptibility or resistance of urinary stones to treatment by shock wave lithotripsy First, we will assess the practical limits of clinical helical CT (HCT) for the detection of structure, shape, and composition in stones. Second, we will explore the relative influence of stone shape/orientation versus their internal composition/structure in their susceptibility to breakage by SWL. This phenomenon is important but has been little studied in natural stones. Third, we will explore the possibility that SW-resistant inclusions within stones are the primary cause of residual fragments in SWL. Finally, we will develop and test a scheme for predicting the fragility of stones to lithotripter SWs using the information available from HCT, and test and refine this scheme using a range of stone types. 7 Aim 1. Determine the degree to which relevant stone analysis can be accomplished using present helical CT technology, including dual-energy helical CT. 7 Aim 2. Determine how critical stone shape relative to SW axis is to stone breakage. 7 Aim 3. Determine if CT can be used to detect SW-resistant inclusions within urinary stones inclusions that will result in incomplete comminution, leaving behind fragments. 7 Aim 4. Develop a scheme for predicting the relative fragility of stones to lithotripsy, and test the scheme for a clinically relevant variety of stone compositions and shapes. This project will provide a sound scientific basis for the development of clinical indicators of stone fragility. We envision that urologists will be able to predict stone fragility from helical CT images with minimal doses of X-radiation and that they will be able to use this information to plan patient treatment. The long-term goals of this work are focused on providing a sound experimental basis for prediction, so that future clinical studies can be done with proper knowledge of the potential abilities of clinical equipment and proper knowledge of how to apply these abilities. Shock wave lithotripsy doesn't always work to break up a kidney stone, and shock waves can injure the kidneys and may have long-term effects on health. Experimental evidence suggests that CT (CAT scan) can describe the shape, position, composition, and structure of stones so that shock wave-resistant stones can be identified. We aim to study this possibility in detail, and provide a step-by- step guide to the use of CT for identifying which stone patients should be treated with shock wave lithotripsy.